Abstract

Application of speckle variance optical coherence tomography (OCT) to endovascular imaging faces difficulty of extensive motion artifacts inherently associated with arterial pulsations in addition to other physiological movements. In this study, we employed a technique involving a fourth order statistical method, kurtosis, operating on the endovascular OCT intensity images to visualize the vasa vasorum of carotid artery in vivo and identify its flow dynamic in a porcine model. The intensity kurtosis technique can distinguish vasa vasorum from the surrounding tissues in the presence of extensive time varying noises and dynamic motions of the arterial wall. Imaging of vasa vasorum and its proliferation, may compliment the growing knowledge of structural endovascular OCT in assessment and treatment of atherosclerosis in coronary and carotid arteries.

Stationary EV-OCT image of porcine carotid artery when the imaging catheter is placed close to the vessel wall (Media 4). The supposed vasa vasorum is indicated by the white arrow. Scale bar = 1mm. Inset is the zoomed in version of the red box.

Kurtosis signal map of porcine carotid artery when the imaging catheter is placed close to the vessel wall (Media 5). The vasa vasorum is indicated by the white arrow. The flowing of blood clot debris is also visible near the vessel wall and the lumen. Scale bar = 1mm. Inset is the zoomed in version of the red box.

Average intensity of a region of interest around the vasa vasorum and an arbitrary section of the vessel wall versus time. Although periodic variation in intensity is also observed in the vasa vasorum, these intensity fluctuations are of the same approximate value, making it extremely difficult to identify vessel wall structures such as the vasa vasorum micro-vessels (Media 4).

Average speckle variance of suspected vasa vasorum region and arbitrary vessel wall versus time. At the vasa vasorum, misleadingly, the speckle variance is much larger due to its proximity to the imaging catheter. Speckle variance was computed within a moving time window of 8 frames, updated at 100fps.

Average kurtosis of suspected vasa vasorum region and arbitrary vessel wall versus time. At the vasa vasorum, the kurtosis is much larger due to pulsation of blood filling and emptying the micro-vessel. Note the increase in pixel intensity of the vasa vasorum region, which acts as a contrast mechanism such that these vessels become visible and stand out when compared to the surrounding tissue (Media 5). Kurtosis was computed within a moving time window of 32 frames, updated at 100fps.